Loading systems of the above-mentioned type are known, in particular from documents U.S. Pat. No. 4,827,829 and EP-0 004 581.
In document U.S. Pat. No. 4,827,829, the chamber pivots in a vertical plane about a horizontal axis in alignment with the trunnion axis of the gun. Whatever the elevation angle of the gun, the chamber, when in its loading position, is always in alignment with a vertical axis, and the new round is loaded through the bottom opening of the chamber. In other words, the pivot angle of the chamber varies as a function of the elevation angle of the gun, and it is always equal to the complementary angle to the elevation angle. The feed device and the device for loading a round into the chamber (not described in detail in that document) are secured to a stationary support, and it is merely specified that they do not include a flexible coupling device between the loading device and the breech assembly of the gun for compensating variations in the elevation angle of the gun between two round loading operations. It should be observed that in that document, a round can be loaded into the chamber only after the gun has returned to the battery position, thereby reducing firing rates.
In document EP-0 004 581, the chamber pivots through 360.degree. in steps of 90.degree.. In other words, after pivoting through 90.degree., the chamber has passed from a firing position to a loading position, or vice versa. The chamber pivots in a vertical plane about an axis parallel to the trunnion axis of the gun. Rounds are stored in a magazine in the form of a bar situated above the chamber. Rounds are disposed vertically and they are loaded one by one by means of a lever when the chamber is in one of its two loading positions, both of which positions are in alignment along a vertical axis perpendicular to the axis of the barrel.
The magazine is linked in translation to the chamber and a round is loaded during the return stage of the recoil motion of the gun. In general, the system described in that document requires large amounts of volume that are incompatible with it being used for a medium caliber gun, in particular when mounted on an armored vehicle. Furthermore, the displacement of the feed device during the recoil motion of the gun is detrimental to proper operation thereof.